This application claims the priority of Austrian utility model no. GM 546/2001, filed Jul. 10, 2001, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a track work machine which is mobile on a track and includes a machine frame supported on the track by undercarriages and having an excavating device with a ballast pick-up unit arranged underneath the track.
A track work machine of this kind is described in Japanese publication No. JP 2000257003 A. Arranged at the rear end of the machine frame is an excavating device, which is formed by an endless clearing chain looped around the track during working operations. The clearing chain is arranged so as to protrude from the machine frame beyond the rear undercarriage and designed to be pivotable upwards by means of a complicated structure to assume an inoperative position on the machine frame during transit travel of the machine.
Japanese publication No. JP 2000290904 A describes a track work machine with an excavating device with no separate apparatus for adjusting the excavating device. In order to prevent the clearing chain from being subjected to excessive load during working operations, it is necessary to provide additional support rollers, running on the track, which are situated in front of the excavating device with regard to the operating direction.
Austrian Pat. No. AT 387 999 B describes a large, high-efficiency ballast cleaning machine having an excavating device positioned between undercarriages supporting the machine frame on the track. One of these undercarriages, arranged centrally, is designed to be adjustable in the direction of longitudinal extension of the machine relative to the machine frame in order to thereby extend the construction area or renewal gap during working operations. With this design, it is possible to lift the track to a higher extent, and to achieve a more gentle deflection curve of the rails during the track lifting process.
It would be desirable and advantageous to provide an improved track work machine of the afore-described type, which has a compact configuration and simple construction while still being reliable in operation.
According to one aspect of the present invention, a track work machine includes a machine frame extending longitudinally in the direction of the track and having a front end and a rear end with regard to an operating direction of the machine, an excavating device mounted at the rear end of the machine frame and having a leading ballast pick-up unit, which is arranged underneath the track, and a trailing discharging end, a conveyor belt associated with the discharging end and provided for receiving and transporting excavated ballast, and a front undercarriage and a rear undercarriage for support of the machine frame on the track, wherein the rear undercarriage is mounted on the machine frame for displacement in the longitudinal direction from a transit travel position, in which the rear undercarriage is situated between the discharging end and the ballast pick-up unit of the excavating device, in the direction towards the front undercarriage.
The present invention resolves prior art problems associated with an excessive overhang, i.e. the portion of the machine projecting over the undercarriage situated at the end, without adversely affecting the efficiency of the excavating device during operation, by providing a displaceable design of the rear undercarriage. Required retooling operations on the machine can be reduced to a minimum in an ergonomically advantageous way that also adds to the operator""s safety.